As a conducting material, a polymer film or a polymer sheet having a highly conducting inorganic particle is one of the important materials and technical fields of the industry. Some of the present inventors propose efficient production of a cellulose nanofiber (Patent Document 1), and a conductive film formed of a water-dispersible polymer in which the cellulose nanofiber is dispersed in a conductive polymer (Patent Document 2). The cellulose nanofiber is electrically insulating. Nevertheless, some of the present inventors suggest that the combination of the cellulose nanofiber with the conductive polymer improves the conductivity of the composition.